I would go with scoutt on the Esc while loading up thing. Perhaps it doesn't work on ME. I've never used ME and don't plan on ever using it if I can help it.

Instead of that, perhaps you can confirm each command one by one until you find out where the computer is hanging - press F8 after the BIOS has finished doing its stuff and the OS has started up, and you should get a boot menu where you can choose step-by-step confirmation. Well maybe that doesn't work on ME either but I think it should. This is why I don't want to use ME, because it's designed to stop people doing anything remotely complicated as far as I can tell.

The fact it's assembled by Gateway should make absolutely no difference whatsoever. All Gateway do is get some components and stick them together, then put a 'Gateway' label on the box and sell it to you. There is nothing particularly special about the brand name of a PC. If all Gateway PCs have some strange common setup though, I guess that could make a difference, but this doesn't sound like something that's down to the way Gateway configured it.